Shadow mask aperture and phosphor dot arrangement in two color cathode ray tube

ABSTRACT

An aperture mask and patterned screen combination is provided for use in a two beam shadow mask type of color cathode ray tube. The mask is utilized in the formation and subsequent operation of the patterned screen including a repetitive array of two phosphor areas. The multitude of apertures defined by the interstitial webbing of the mask member are arrayed in a plurality of parallel rows having given directional orientations. Any three mutually adjacent apertures in any two adjacent parallel rows are oriented to form an isosceles right triangular relationship. The resultant screen associated therewith exhibits enhanced resolution and brightness.

I SHADOW MASK APERTURE AND PI-IOSPHOR DOT ARRANGEMENT IN TWO COLOR CATHODE RAY TUBE [111 3,843,900 Oct. 22, 1974 Primary Examiner-Robert Sega! Attorney, Agent, or Firm-N0rman J. OMalley; Cyril ;F d k H. R' 75 Inventor: Donald L. Say, Waterloo, NY. Kramer re em 7 [73] Assignee: GTE Sylvania Incorporated, v

Stamford, Conn BSTRACT [22] Filed: May 22, 1973 An aperture mask and patterned screen combination is provided for use in a two beam shadow mask type of [21] Appl' color cathode ray tube. The mask is utilized in the for- Related U.S. Application Data mation and subsequent operation of the patterned [62] Division of Ser. No. 273,158, July 19, 1972, Pat. No. Screen including a repetitive array OfIWO P P 3,777.202, which is a division of Ser. No. 153,695, 835. The multitude of apertures defined by the intersti- June 16, 1971, Pat. No. 3,720,854. tial webbing of the mask member are arrayed in a plurality of parallel rows having given directional orienta- [52] U.S. CI. 313/408, 313/470 tions. Any three mutually adjacent apertures in any [5]] Int. Cl. H01j 31/20, I-lOlj 29/32 two adjacent parallel rows are oriente'dto form an [58] Field of Search 313/92 B, 85 S isosceles right triangular relationship. The resultant screen associated therewith exhibits enhanced resolu- [56] References Cited tion and brightness. FOREIGN PATENTS OR APPLICATIONS 1 Cl 3 D F; 117,065 11 /I964 France 3l3/85 s rawmg gums N O K 29 Cl L I P R i D '8 \G v M B" 49 '1 I 5 I 5;! R T A R b f G 5, 2s e. 1 G ai Q' a 43 1 i x R 4' J. K l G NI 0 K G K 5 A Q K g I M,

PATENTEBnmzz um sum 11! 2 PRIOK ART SHADOW MASK APERTURE AND PHOSPHOR DOT ARRANGEMENT IN TWO COLOR CATHODE RAY TUBE CROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION This invention relates to cathode ray tubes and more particularly to a color cathode ray tube shadow maskscreened panel combination.

In certain types of information display systems, wherein specific data for comparative purposes is visually evidenced, it is desirous to present the various data factors in a vivid luminous manner. In some applications a limited number of simultaneous color or hue differences are adequate for the presentation of an evaluation displaay. For this type of system, a so-called two color cathode ray tube is appropriate. Such a tube normally utilizes two electron beams and a patterned screen formed of a repetitive array of two separate phosphor areas from which the additive aspects of a composite hue may also be obtained. A conventional shadow mask tri-color tube can be adapted for this usage by eliminating one of the three electron guns and the associated phosphor component in the screen pattern. However, when such is done, the blank areas in I the screen are detractive factors affecting both the resolution and the brightness of the display. Thus, it has been found that the aperture arrangement in the conventional tri-color shadow mask tube cannot be effectively utilized to produce an efficient two-phosphor screen of the quality required for the display applicatron.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide an improved shadow mask-screen combination for a cathode ray tube having an aperture array appropriate for effecting an efficient two-phosphor patterned screen exhibiting enhanced resolution and improved brightness.

Another object is to provide an improved apertured shadow mask and a two-phosphor screened panel combination for use in a two beam cathode ray tube.

The foregoing objects areachieved in one aspect of the invention wherein an improved shadow mask exhibiting a discrete aperture arrangement is combined with a patterned screen including a repetitive array of two phosphor areas for use in a cathode ray tube employing two electron beams. The foraminous mask member of the combination comprises a multitude of apertures which are defined by the interstitial webbing and arrayed in a substantially uniform pattern effecting a plurality of parallel rows of given directional orientations. Any three mutually adjacent apertures in any two adjacent parallel rows are oriented in a related manner to form an isosceles right triangular relationship. The patterned screen formed and associated in combination with the aperture array of this mask exhibits a lumines- Y axial direction are cent display having markedly enhanced resolution and brightness.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged fragmentary plan view illustrating a prior art relationship of the mask apertures with the associated patterned screen;

FIG. 2 is a partial perspective view showing the screen, shadow mask and electron gun relationships of a tube embodying the invention; and

FIG. 3 is an enlarged fragmentary plan view illustrating the patterned screen and mask aperture relationship of the invention taken along the line 3-3 in FIG. 2 as viewed from the orientation of the source of the electron beams.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings.

The descriptive phraseology two-color cathode ray tube as used in this specification refers to a tube employing two separate electron beams and a patterned cathodoluminescent screen comprising a repetitive array of two phosphor areas. Each of the phosphor areas is made up of one or more phosphor materials which, when excited, emits a'distinctive hue. Simultaneous excitation of both phosphor areas produces a third color formed as an additive composite hue. By

wa of exam le, reen G and red R luminescent dots will be described herein.

With reference to the drawings, there is shown in FIG. 1 an enlarged fragmentary plan view of a prior art aperture mask 11 and associated patterned screen 13 relationship as viewed from the source of electron beams within the tube. The foraminous shadow mask member 11 has therein a multitude of apertures 15 defined by the opaque interstitial webbing-l7 and presents an aperture array as employed in a conventional tri-color or tri-dot color cathode ray tube. The aperture array is directly related to the X and y axes of the mask and the diagonals associated therewith. For example, IIII QQ IQ E FPFF W n ll/9 jacent parall rows Y-Y and G G, having centers 1, m, and 0, form an equilateral triangle 1m0 wherein all three sides are of equal lengths and included angles are 60, therefore 48 Ad). In considering adjacent parallel rowsX-X' and EE', the adjacent apertures having centers o," m," and n form an isoceles' triangle omn. While related triangles lmo and omn has a common side om and equal sides om" and mn, they are otherwise respectively dissimilar: 60, while 4gb LB 60, whereas 43 30; and side 10 is shorter than side on. In view of the unlike triangular relationships, the linear spacings t between apertures in the rows oriented in the Y-Y. direction are equal to the linear spacings between apertures in the rows oriented in the diagonal W-W' and J-J directions, while the aperture spacings w in the X-X' directional orientation are greater. In similar manner the color repeat spacings v" between adjacent parallel rows of apertures in the greater than the row spacings s in the X direction. 1

The two-color screen 13 formed on the glass substrate or receiving panel 19 and operationally associated with the prior art mask 11 is comprised of pairs of G' and R phosphor areas. Since the third phosphor color area has been eliminated from this two-color screen 13, the panel area 21 usually covered'by the third phosphor is free of phosphor material in the screen pattern 13 shown: Thus, it is clearly evident that high resolution and brightness cannot be expected from the aforedescribed prior art screen 13 wherein over one-third of the panel screen area is free of phosphor material.

In reference to FIG. 2, a partial perspective view denotes portions of a'cathode ray tube 25 enclosed by a 'fragmentarily shown envelope 27 wherein the viewing panel 19 has a two-color screen pattern 29 in the form of repetitive pairs of contrasting phosphor areas disposed in rows thereon. A metallic foraminous shadow mask 31 is spatially positioned relative to the screen 29 being directly associated with the formation and subsequent operation of the patterned screen. in usage, the apertured shadow mask 31 and screened viewing panel 19 are considered as a combination assembly 33, and as such are conventionally spatially affixed by means not shown. Additionally, predeterminately positioned within the envelope 27 is a source of electrons 37 oriented in a manner to direct two separate electron beams 39 and 41 toward the apertured shadow mask 31 and the related screen 29. As shown, the electron beams 39 and 41 converge at the mask 31 passing through an aperture 43 therein and thence selectively impinging and exciting separate phosphor areas of the screen 29 to provide a luminescent display.

In greater detail, reference is made to FIGS. 2 and 3 wherein the shadow mask 31 comprises a multitude of apertures 43 defined by the opaque interstitial webbing 45. The apertures are arrayed in a substantially uniform pattern being adjacently related in a manner to effect a plurality of rows which, in turn, define a plurality of linear directional relationships such as, CC, YY', LL and K-K. The rows of a given directional ,orientation are substantially parallel, as for examplei X-X' and A-A', Y-Y' and C-C', LL' and M-M, and KK' and N-N'. The rows X-X and Y-Y' define the respective X and Y axial directions in the shadow mask member 31.

Any three mutually adjacent apertures in any two adjacent parallel rows are substantially oriented in an isosceles right triangular relationship. For example, three mutually adjacent apertures, having centers of a, b," and c" respectively, are oriented in adjacent parallel rows Y-Y and C-C, in OO' and L'L, and in NN' and KI('. The resultant triangle abc includes a right angle A and an acute angle A of 45. Since the acute angles are complements of each other, the remaining acute angle is also 45, and therefore the respective sides ab and cb" are equal; consequently, the spacings p" and q between adjacent diagonal rows are also equal. A similar isosceles right triangle t-bd is formed of the three mutually adjacent apertures 43 having centers c," 17,? and d which are oriented in adjacent parallel rows X-X' and A--A', in L-L' and MM', and in NN and KK. The two isosceles right triangles abc" and Cb are equal since they have a common sid cb" and angular equalities, i.e. A A, Q and The hypotenuse ac of triangle abc is definitive of the Y axial direction in the mask, and the counterpart hypotenuse cd of triangle cbd" is definitive of the X axial direction. In each of the respective triangles abc" and cbd, the sides forming the right angle, for example, in abc, sides ab and cb" forming the right angle 4, define the diagonal directions NN and L-L in the mask, each diagonal being associated with the respective X and Y axes in substantially 45 angular relationships. The described diagonal relationships diametrically divide each of the apertures 43 into four substantially equal segments 49, 50, 51 and 52.

The linear spacings h and f between the individual mask apertures in the rows directionally associated with both the X and Y axes are substantially equal since the hypotenusal sides (10" and cd" of similar triangles abc and chef are of equal lengths. The spacings e and g" between adjacent parallel rows, of apertures, such as XX', A-A and Y-Y' and CC, in both the X and Y directions are equal in view of the equali ties of dimensions f? and bj each being normal to the midpoints of the hypotenusal sides ac and cd of the similar triangles abc and cbd. Therefore, the spacings e and g" between adjacent parallel rows of apertures, which are in effect color repeat dimensions, associated with both the X and Y axial directions are advantageously equal; and in addition, these spacings 2" and g are equal to substantially one-half the respective linear spacings f and 11 between the apertures in the respective rows in view of the equalities of the aforementioned triangular dimensions whereof, iajI $jC!3 6$CjI$9 $6jIdY! The improved shadow mask 31 of the invention has more apertures per area or greater transparency than does the described prior art mask 11, and therefore the improved mask 31 affords higher resolution and enhanced brightness by permitting the passage of a greater density of exciting electronsln considering the greater transparency of the improved mask 31, attention is drawn to FIG. 3 wherein the aforedescribed triangular area abd is referenced. For purposes of example, the following values are ascribed:

Aperture dia. k" 0090 ac or f .0250" "jb" or "g" .0125" color repeat spacing for both X and Y axes Improved Mask Transparency Aperture dial "it" .0090" 10" or r" .0217" v X axis color .0188" repeat spacing .S Y axis color .0108" I repeat spacing Prior art mask transparency With reference to FIGS. 2 and 3, the two-color screen pattern 29 comprises a repetitive array of two phosphor areas or dots-which are substantially equally adjacent to one another, being disposed in accordance with the aperture array of the mask 31. The two phosphor areas, in this instance, are conventional cathodoluminescent materials such as those that emit green G or red R" luminous hues when electron excited. The two phosphor areas, G", R" are alternately and adjacently disposed in substantially linear parallel rows in both horizontal and vertical X and Y, directional relationships in the screen 29. In the X axis directional relationship, the phosphor rows are oriented in a manner that the linear diametrical axes of the phosphor dots Z-Z' and that of the apertures XX' are substantially coincidental. There are no large vacant areas 21 in the screen as are evidenced in the prior art screen 13 in FIG. 1.

As shown, the phosphor areas G, R have a diameter i" which is greater than the diameter k of the related aperture. Such diametrical relationship is .not intended to be limiting, as the dots may also be of a size equal to or smaller than the apertures and still be in keeping with the concept of the invention. There may be instances when it is desirous to form a screen pattern array wherein the individual phosphor areas are 'disposed in an equidistant spaced-apart relationship. Such alteration of the pattern spacing could necessitate a proportional modification of the triangular dimensions between the apertures in the mask, however, the'dimensional relationships therebetween would remain substantially constant in keeping with the teaching of the invention.

In FIG. 2, the source of electrons 37 is an electron gun structure assembled in a manner to provide and direct two separate electron beams 39, 41 to the maskscreen portion 33 of the tube 25. The individual beams are controlled to selectively excite a respective one of the two phosphor areas G, R in a predetermined sequence to provide a luminescent display in the twocolor screen 29. As indicated, the directional line of scan S-S of the two beams 39, 41 is substantially parallel with the X-X axial orientation of the mask apertures 43 and such is preferred; but there may be occasions when the electron beams are oriented to scan the mask 31 and associated screen 29 in a modified manner. It has been found that the line of scan S-S' can be shifted clockwise or counter-clockwise with reference to the X-X of the mask, but such deviation should not exceed a substantially 45 angular relationship with the X-X axis of the mask.

Thus, there is provided cathode ray tube shadow mask and screened panel combination whereof the mask has a discrete aperture array for effecting the efficient twophosphor patterned screen for use in a twobeam tube. The resultant luminescent image exhibits enhanced resolution and improved brightness.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A shadow mask and screened viewing panel combination for use in a color cathode ray tube utilizing two electron beams to produce a luminescent screen display, said combination comprising:

a metallic foraminous shadow mask member wherein the multitude of apertures defined by the interstitial webbing are arrayed in a substantially uniform pattern, said apertures being adjacently related in, a manner to effect a plurality of rows defining a v plurality of linear directional relationships, said rows of a given directional orientation being parallel, any three of said mutually adjacent apertures in any two adjacent parallel rows being oriented in an isosceles right triangular relationship, the hypotenusal sides of said triangles defining X and Y axial directions in said mask member, the right angular related sides of said triangles defining 45 degree diagonal relationships of said apertures with said axes, the spacings between adjacent parallel rows of apertures associated with both the X and Y axes being equal to substantially one-half the linear spacing between the apertures in said rows directionally associated with both of said axes; and

a cathodoluminescent screen formed on said viewing panel adjacent to said apertured shadow mask, said screen being dot-patterned with a repetitive array of two phosphor areas substantially equally adjacent to one another being disposed in accordance with the aperture array of said mask, said two phosphor areas being alternately and adjacently disposed in a similar manner in linear parallel rows in both horizontal and vertical directional relationships in said screen; said mask being spacedlyv af-' fixed to said screened panel to provide a combination assembly.

o-ww UNITED sTATEs PATENT OFFICE A CERTIFICATE OF CORRECTION Pacent 2 10, 3,843,900 Dated October 22 1974 Inventor) Donald .L. Say

It is certified that error appears in the above-identified patent and that aa'id Lettets Patent are hereby corrected as shown below:

Column 3 Line 66: 4 ,9" should ad I Q=' Q' Signed and sealed this 24th day of December 1974.

(SEAL) Attest McCOY M. GIBSON JR; C. MARSHALL DANN Attes ting Officer Commissioner of Patents 

1. A shadow mask and screened viewing panel combination for use in a color cathode ray tube utilizing two electron beams to produce a luminescent screen display, said combination comprising: a metallic foraminous shadow mask member wherein the multitude of apertures defined by the interstitial webbing are arrayed in a substantially uniform pattern, said apertures being adjacently related in a manner to effect a plurality of rows defining a plurality of linear directional relationships, said rows of a given directional orientation being parallel, any three of said mutually adjacent apertures in any two adjacent parallel rows being oriented in an isosceles right triangular relationship, the hypotenusal sides of said triangles defining X and Y axial directions in said mask member, the right angular related sides of said triangles defining 45 degree diagonal relationships of said apertures with said axes, the spacings between adjacent parallel rows of apertures associated with both the X and Y axes being equal to substantially one-half the linear spacing between the apertures in said rows directionally associated with both of said axes; and a cathodoluminescent screen formed on said viewing panel adjacent to said apertured shadow mask, said screen being dotpatterned with a repetitive array of two phosphor areas substantially equally adjacent to one another being disposed in accordance with the aperture array of said mask, said two phosphor areas being alternately and adjacently disposed in a similar manner in linear parallel rows in both horizontal and vertical directional relationships in said screen; said mask being spacedly affixed to said screened panel to provide a combination assembly. 